Technical Abstract:
Treatments known to inhibit or delay ripening were applied to imported 'Kent' and 'Tommy Atkins' mangoes. Mangoes that were fairly firm, with some ground color development ('Kent') or hard with slight color blush ('Tommy Atkins') were treated with 1-methylcyclopropene (1-MCP) at 25 ppm for 24 or 12 hours, respectively, ethanol (5.0 g kg fruit-1) for 24 or 8 hours, respectively, and heat (38 °C, 98% RH) for 24 or 12 hours, respectively. Treated fruit were cut 24 hours after treatment, and stored at 7 °C for 12 ('Kent') and 14 ('Tommy Atkins') days. Ethanol treatments increased fruit firmness in both cultivars. Ethanol treatment for 24 hours on 'Kent' maintained higher firmness, L* value, and visual quality in storage. Heat vapor increased softening in both cultivars, and decreased visual quality in storage for 'Kent'. Ethanol and acetaldehyde content were higher in heat- and ethanol-treated fruit. However, levels decreased in storage when fruit were exposed to ethanol for 8 hours as opposed to 24 hours. Higher ethanol content in the fruit correlated with off flavor. 1-MCP was effective at retarding ripening of 'Tommy Atkins' but not 'Kent', but the level used, 25 ppm, cannot be applied by the industry as it has only been registered for use on fruit at 1 ppm. Therefore, ethanol treatments for 10 and 20 hours were repeated on 'Kent' fruit harvested from a commercial orchard in Homestead, Florida. The effect of quarantine heat treatment, and maturity at the time of ethanol application were also investigated. Mangoes at the "green" and "with shoulders and slight blush color" maturity stages were maintained in a water bath at 46 °C for 1 - 1.5 h, depending on fruit size. Fruit were treated with ethanol at the beginning of background yellow color development (maturity 1, less ripe) or fully colored (maturity 2, ripe). The heat treatment tended to synchronize fruit ripening. Ethanol reduced respiration rate of whole mangoes immediately after treatment, independently of prior heat application or maturity stage. However, this effect did not carry over to cut fruit in storage, except on maturity 2, heat-treated mangoes. Ethanol treatment for 20 hours had the most significant effect on maturity 1, heat-treated fruit. This resulted in higher firmness, titratable acidity, L* and hue angle, and lower pH and a*. There were no significant differences between treatments for sugar content. Taste panels showed that fruit treated with ethanol vapors for 20 hours at maturity 1 were the firmest and tartest, had the least mango flavor and the most off-flavor, and were least preferred. Like in the earlier study, fruit treated with ethanol for 20 hours had high levels of internal acetaldehyde, ethanol and ß-pinene. Ethanol vapor on whole fruit may improve quality of cut mangoes in terms of surface color and firmness, but impart unacceptable off flavor if exposure is over 20 hours.